thats not exactly how it works. The Halloween Mask leopard gecko is a Very bold project paul Allen and Albey have been working on for years. Line breeding for bolder pattern and head pattern. If you search there is a post on here explaining it better.
I believe he is refering to "Halloween", not "Halloween Masks". If you breed a Tang to a Boldstripe, eventually you'll get boldtangs--geckos displaying both the Tang (orange) trait AND the Bold (black) trait...(i.e. Halloween) The halloween masks are something entirely different, and they are way cool...